Analysis of factors affecting power system normal form results

This paper discusses the experience in the use of normal form (NF) theory to study nonlinear modal behavior in stressed power systems. Making use of NF theory, we examine the use of several analytical indices to quantify system nonlinear modal interaction and discuss major factors affecting NF results and interpretation. Specifically, the influence of the initial conditions and the effect of strong modal resonance on the normal form analysis is studied. Based on this understanding, heuristic criteria for guessing initial conditions area devised for assessing model adequacy. New insights into the nature of system oscillations are offered and criteria for characterizing nonlinear effects are discussed. The analysis of factors affecting NF results is illustrated on a four-machine two-area test power network. Numerical calculations are presented and discussed to check the accuracy of the method analysis. (C) 2004 Elsevier B.V. All rights reserved.